It depends on what you're trying to do.
If I were in your position, I'd concentrate on shoring up HTML knowledge, with emphasis on cross-browser and accessibility. Combine that with CSS, since you'll need CSS if you want to move/stay away from having to rely exclusively on tables for layout.
Then, if you want to concentrate on front-end design work, go for JavaScript/DHTML/Ajax. You could learn JavaScript basics, then hone your skills at finding and customizing DHTML scripts that do what you want them to. There are enough snippet libraries and code sites out there that it's possible to add lots of nice, useful effects to your site without having to write the code from scratch. (Just watch out for cross-browser compabitility and interaction problems between scripts.)
If you want to concentrate on back-end development, learn PHP and the basics of *SQL. If you learn better by doing, try to find books or courses that are hands-on or that have you build an application to learn the skills. Again, there are the usual script archives you can plumb to find some PHP to backwards-engineer. Just make sure to learn from solid, securely-written scripts to pick up good habits.
That's what I've done, in which order, and why. Your mileage may vary, especially if you want to concentrate on back-end programming rather than front-end/JS/Ajax.